Frequency and voltage dependence of dielectric properties, complex electric modulus, and electrical conductivity in Au/7% graphene doped-PVA/n-Si (MPS) structures

In order to increase the capacitance of Au/n-Si (MS) structure, 7% graphene doped PVA was coated on n-Si as an interfacial layer. The measured data of capacitance (C) and conductance (G/omega) of Au/7% graphene doped-PVA/n-Si (MPS) structure was utilized for the calculation of real and imaginary parts of complex permittivity (epsilon* = epsilon' - j epsilon ''), loss tangent (tan delta), complex electric modulus (M* = M' + jM ''), and electrical conductivity (sigma). The admittance measurements (C and G/omega) were carried out in the frequency range of 0.5 kHz to 1 MHz at room temperature. Frequency dependence of the dielectric constant (epsilon'), dielectric loss (epsilon '') and tand shows a dispersive behavior at low frequencies. This behavior was explained by Maxwell-Wagner relaxation. Due to the dipolar and the interfacial polarizations, as well as the surface states (N-ss) and the interfacial PVA layer, the parameters exhibited a strong dependence on frequency and applied bias voltage. The sigma versus log(f) plot exhibited both low and high frequency dispersion phenomena such that at low frequencies sigma value corresponding to the dc conductivity (sigma(dc)), but at high frequencies it corresponds to the ac conductivity (sigma(ac)). M' and M '', both, have low values in the low frequency region. However, an increase is observed with the increasing frequency due to the short-range mobility of charge carriers. As a result, the change in dielectric parameters and electric modulus with frequency is the result of relaxation phenomena and surface states. (C) 2016 Wiley Periodicals, Inc.